Detection of a detection target labeled with a fluorescent pigment is performed such that the fluorescent pigment is irradiated with excitation light having a specific wavelength, fluorescence emitted from the fluorescent pigment is received, and thus the detection target is detected. In this process, a higher fluorescence intensity makes the detection of the target easier. It has been desired to enhance the detection sensitivity.
Accordingly, to enhance the detection sensitivity, a method has conventionally been used in which, for example, a reflector is provided on an inner wall of the detection unit to cause the reflector to reflect fluorescence emitted from the fluorescent pigment, and thus to condense the fluorescence onto a light reception unit.
Meanwhile, a method for enhancing fluorescence has recently been developed in which a mixture of a fluorescent pigment-containing solution and a fluorescence-enhancing diluent is applied to a biological tissue section to fluorescently stain the biological tissue section, and thus enhanced fluorescence is obtained (Patent Document 1).
This method uses, as the fluorescent pigment, indocyanine green, which is a near-infrared fluorescent pigment, and uses, as the fluorescence-enhancing diluent, an emulsion such as milk, formula milk, fat emulsion, soybean oil, or egg phospholipid, or Intralipid, Lyposyn, Nutralipid, Soyacal, Travamulsion, SOMFlipid, Clinoleic, or Lipovenoes, which are registered trademarks.
Patent Document 1 mentioned above describes that when a biological tissue section was stained with a mixture of a fluorescent pigment and a fluorescence-enhancing diluent, and was then irradiated with near-infrared radiation, an observation showed that the fluorescence intensity was increased 5 to 20 times higher than the fluorescence intensity obtained without addition of the fluorescence-enhancing diluent.